DESCRIPTION (Applicant's Description Verbatim): Our goal is to obtain registration of a low antigenicity recombinant fVIII product for the treatment of patients with neutralizing antibodies against human fVIII. Such inhibitor patients include those with hemophilia A who develop alloantibodies when treated with replacement human fVIII, as well as patients with "acquired hemophilia" who develop autoantibodies against endogenous fVIII. The development of an inhibitor to Will is a serious, potentially life threatening condition. Current treatment options are limited to so-called "bypassing" agents" and plasma derived porcine fVIII (Hyate:C). Bypassing agents are nonphysiologic and occasionally cause overdrive of the coagulation cascade. This may result in severe complications, such as disseminated intravascular thrombosis or myocardial infarction. Use of Hyate:C is currently limited by regulatory, treater and patient concerns arising from the plasma source of the product and side effects attributable to the relative impurity of the product. Applicant has exclusive access to recombinant porcine fVIII. Applicant has obtained substantial in vitro and in vivo data that supports the suitability of recombinant porcine Will for development as a low antigenicity fVIII product. Phase II of applicant's SBIR project shall include: completion of the preclinical development of the product, submission of an IND to the FDA, and initial safety and efficacy studies of the product in hemophilia A patients. In the preclinical stage, the safety and immunogenicity of the product will be studied in mice and cynomolgus monkeys. Pharmacokinetic data will be obtained in a highly predictive dog model of hemophilia A. After an ND is filed, the safety and pharmacokinetics of the product will be studied in a clinical trial in which approximately twelve inhibitor patients shall receive the product. PROPOSED COMMERCIAL APPLICATION: Approximately 26% of all hemophilia A patients develop antibodies. A significant portion cannot successfully be treated with human fVIII. A recombinant, low antigenicity fVIII product would compete well in the fVIII inhibitor patient market and be a first line therapy for "acquired hemophilia."